Method of making aluminum alloy conductor

ABSTRACT

An electrical conductor with improved toughness and workability is made by adding about 0.01 percent tin to high-iron content, zinc bearing aluminum to be hot-rolled from cast bars. Insulated cables are made comprising the improved conductors.

United States Patent [191 Medrick et al.

METHOD OF MAKING ALUMINUM ALLOY CONDUCTOR Inventors: Donald S. Medrick, Woodbury,

Conn; Clermont J. Snyder, New York, N.Y.; James E. Teague,

Sycamore, I11.

Assignee: The Anaconda Company, New

York, NY.

Filed: July 5, 1973 Appl. No.: 376,480

Related U.S. Application Data Division of Ser. No. 146,219, 1. v

U.S. Cl 29/527.7, 75/138, 148/2 Int. Cl; 823p 17/00 Field of Search 29/1835, 193, 527.7;

[451 July 2, 1974- 56] References Cited UNITED STATES PATENTS 3,063,832 11/1962 Snyder 75/138 3,490,955 1/1970 Winter ct al.. 148/32 3,670,401 6/1972 Schoerner 29/5277 X Primary Examiner-Charles W. Lanham Assistant Examiner-D. C. Reiley, lll Attorney, Agent, or Firm-Victor F. Volk [5 7] ABSTRACT An electrical conductor with improved toughness and workability is made by adding about 0.01 percent tin to high-iron content, zinc' bearing aluminum to be hotrolled from cast bars. Insulated cables are made comprising the improved conductors. I

1 Claim, 3 Drawing Figures METHOD OF MAKING ALUMINUM ALLOY CONDUCTOR This is a division of application Ser. No. 146,219 filed May 24th, 1971.

BACKGROUND OF THE INVENTION In U.S. Pat. No. 3063832, dated Nov. 13, 1962, C. .l. Snyder, one of the applicants in the present case, disclosed a very high purity aluminum conductor in which the conductivity was maintained above 62 percent of the International Annealed Copper Standard (IACS) by the addition of tin. However, it was believed at that time that in order to achieve the advantage of the tin addition the aluminum content would have to be at least 99.5 percent and preferably 99.6 percent. Such high purity aluminum, is, however unduly expensive. R. J. Schoemer, in U.S. Pat. No. 3512221 issued May 19, 1970, taught the use in continuous cast bar of a high iron content aluminum for which he claimed superior elongation. We have found that high iron aluminum without the presently discovered addition of tin is deficiently brittle in such operations as compacting and does not provide consistent 62 percent conductivity in the one-half hard or fully annealed state.

SUMMARY We have invented .an electric conductor which may take the form of bare rod suitable for cold drawing having a diameter of 0.25 to 1.00 inch, cold drawn wires, or stranded pluralities of such wires, but is not limited thereto, and which has minimum 62 percent IACS conductivity at a 16,000 psi tensile strength, consisting essentially of 99.3 to 99.5 weight percent aluminum, 0.3 to 0.45 weight percent iron, at least 0.01 weight percent tin, at least 0.02 weight percent zinc, and the remainder impurities normally present in aluminum of electrical conductivity grade. We have also invented insulated conductors comprising the cold drawn wire of our invention and insulated cables comprising such wires. In making the conductor of our invention we prefer a method whereby an ingot is cast having the above composition, followed by cooling the entire mass to room temperature. The ingots are subsequently reheated to at least 600F and hot rolled to rod having a diameter between one-fourth inch and 1 inch.

BRIEF DESCRIPTION OF THE DRAWINGS:

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS EXAMPLE 1 Analysis by weight: 0.058 percent silicon, 0.420 percent iron, 0.019 percent copper, 0.005 percent manganese, 0.015 percent boron, 0.002 percent vanandium, 0.001 percent chromium, 0.030 percent zinc, 0.009

' percent nickel, 0.005 percent tin, 99.436 percent aluminum, by difference.

The aluminum of EXAMPLE 1 was prepared by melting an EC grade aluminum and adding tin to bring the tin content to 0.01 percent. Thereafter the metal was melted in a crucible 11 (FIG. 2) poured into a mold 12 to form an ingot 13. A large number of the ingots 13 were stored for periods of time sufficient for them to come to room temperature and were stored at room temperature until needed. Thereafter the ingots 13 were transported to a rolling mill where they were heated in a preheating oven 14 to 650F. From the oven 14 the ingots passed through a hot rolling mill 16, emerging therefrom as a rod 17 have a diameter from about 0.25 to 1.00 inch.

The rod 17 is subsequently cold drawn in a conventional manner to form a wire conductor 18 which may be insulated as shown in FIG. 3 with enamel 19 or with an extruded plastic, or stranded with other wires into a stranded conductor 21, insulated, and formed with other such insulated strands, into a cable 22. When the conductor of EXAMPLE 1 drawn to No. 12 AWG was batch annealed to half hard temper the following tensile and elongation measurements were made on three specimens: 15,730 psi and 19.5 percent, 16,100 psi and 18.0 percent, 16,300 psi and 20.0 per cent. Conductivity of all specimens exceeded 62 percent IACS. A creep test was conducted by holding a specimen under a constant 10,000 psi tensile load for 833 hours at room temperature. The total extension so determined was 240 microinches per inch as compared to typical values of 2200 microinches per inch for EC grade aluminum extended similarly for 500 hours.

EXAMPLE 2 Analysis by weight: 0.057 percent silicon, 0.440 percent iron, 0.015 percent copper, 0.005 percent manganese, 0.006 percent boron, 0.001 percent magnesium, 0.003 percent vanadium, 0.001 percent titanium, 0.001 percent chromium, 0.022 percent zinc, 0.011 percent nickel, 0.007 percent tin, 99.431 percent aluminum, by difference. I

Conductor of EXAMPLE 2 was cold drawn to No. 12 AWG and specimens found to have tensile strengths and elongation as follows after continuous annealing: 18,048 psi and 11.0 percent, 18,400 psi and 15.5 percent, 18,196 psi and 12.0 percent, 18,196 psi and 11.8 percent, 16,840 psi and 16.2 percent, 16,840 psi and 16.0 percent. Additional conductor was cold drawn to No. 10 AWG, continuously annealed, and found to have tensile strengths and elongation of 15,570 psi and 18.2 percent, and 16,060 psi and 12.0 percent. Conductivity was in excess of 62 percent IACS.

EXAMPLE 3 Analysis by weight: 0.058 percent silicon, 0.420 percent iron, 0.19 percent copper, 0.005 percent manganese, 0.015 percent boron, 0.002 percent vanadium, 0.001 percent chromium, 0.030 percent zinc, 0.009 percent nickel, 0.005 percent tin, 99. 436 percent aluminum, by difference.

Conductor of EXAMPLE 3 was cold drawn to No. 10

. and No. 12 AWG. Conductor wascold drawn to 0.097

in diameter, seven-stranded together and compacted to 2/0 AWG. No cracking was, experienced during com! pacting. Wire drawn to 0.0975 inch diameter was annealed one-half hard and specimens found to have the EXAMPLE 4 Analysis by weight: 0.051 percent silicon, 0.437 percent iron, 0.016 percent copper, 0.006 percent manganese, 0.010 percent boron, 0.002 percent magnesium, 0.001 percent vanadium, 0.027 percent zinc, 0.004 percent nickel, 0.005 percent tin, 99.441 percent aluminum, by difference.

Conductor of EXAMPLE 4 was hard drawn to No. 13 and No. 19.5 AWG for use as magnet wire. In the hard drawn condition conductivity exceeded 62 percent IACS and after soft annealing the elongation was at least 23 percent.

EXAMPLE Analysis by weight: 0.053 percent silicon, 0.430 percent iron, 0.016 percent copper, 0.006 .percent manganese, 0.011 percent boron, 0.002 percent magnesium,

0.002 percent vanadium, 0.028 percent zinc, 0.004

percent nickel, 0.007 percent tin, 99.441 percent aluminum, by difference.

Conductor of EXAMPLE 5 was hard drawn to No. 13 and No. 19.5 AWG magnet wire. In the hard drawn condition the conductivity exceeded 62 percent, and after soft annealing the elongation was at least 23 percent.

EXAMPLE 6 Analysis by weight: 0.055 percent silicon, 0.391 percent iron, 0.014 percent copper, 0.004 percent manganese, 0.006 percent boron, 0.001 percent magnesium, 0.001 percent vanadium, 0.001 percent titanium, 0.001 percent chromium, 0.025 percent zinc, 0.009 percent nickel, 0.010 percent tin, 99.482 percent aluminum, by difference.

Conductor of EXAMPLE 6 was hard drawn into commercially useful wire, with electrical conductivity of 62 percent in the annealed condition.

The wire cold drawn in EXAMPLE 2-6, was all first cast into ingots, permitted to cool, reheated to at least 600F, and hot rolled into rod prior to cold drawing. We believe that the cooling and reheating steps, when applied to the iron, zinc, tin bearing aluminum of our invention has a hitherto unsuspected effect, the exact mechanism of which is unknown that influences the toughness, high elongation, workability, high conductivity, and very low creep of our conductor. The toughness and workability are manifested by excellent pertor comprising the steps of casting an ingot consisting essentially of 99.3 to 99.5 weight percent aluminum, 0.3 to 0.45 weight percent iron, at least about 0.005 weight percent tin, at least 0.02 weight percent zinc and the remainder impurities normally present in aluminum of electrical conductivity grade, cooling said ingot throughout its entire mass to room temperature,

heating said ingot to at least 600 F, and subsequently hot rolling said ingot to rod having a diameter from A inch to 1 inch, whereby the properties of said conductor will be such that when drawn to No. 12 AWG, annealed to half-hard temper and held under a constant 10,000 psi tensile load for 833 hours at room temperature it will not creep substantially more than 240 mi- 

